Dolphin virus spreads south, may be infecting whales

Saturday

A massive, widespread dolphin plague has reached beaches as far south as Florida, but the majority of recent mortalities washed ashore in North Carolina, experts said this week.

A massive, widespread dolphin plague has reached beaches as far south as Florida, but the majority of recent mortalities washed ashore in North Carolina, experts said this week.

“We’re getting 10 to 20 animals in a week right now,” said Bill McLellan, coordinator for the state’s Marine Mammal Stranding Program and a research biologist with the University of North Carolina Wilmington. “It’s squarely here.”

Since July 1, more than 850 bottlenose dolphins have been found on beaches along the East Coast. More than 100 of those surfaced in North Carolina, all in the past two months. The deaths are attributed to a resurgence of morbillivirus, a measles-like illness that killed 50 percent of the Atlantic dolphin population in a similar outbreak in 1987. Biologists don’t know for certain how many dolphins have died this time around — a high number of carcasses are snatched up by sharks before they reach the beach — but statistically, it’s likely a similarly large number.

“We figure if we get 25 percent of the mortality total, we’re doing really well. So, these are the 850 carcasses we’ve gotten a hold of,” McLellan said. “You multiply that out, the numbers get larger quickly.”

The widening reach of the virus indicates that it’s transitioned from one dolphin population segment to another, a sign that the infection is likely to keep spreading for the foreseeable future.

“The animals are keeping it with them as they migrate south,” McLellan said. “We were hoping the mortality would sort of literally burn itself out over the end of the summer — that the animals susceptible to it would succumb. This is an indication that it’s going to stay in these populations, and now we’re in that position of it transitioning into new stocks of dolphins.”

The response to stranding’s has kept North Carolina’s Marine Mammal Stranding Program network overworked.

North Carolina would normally expect to see about two stranding’s a week and is now seeing four or five times that.

“It’s stretching everybody’s resources,” McLellan said.

In the southern area of the state, from about Camp Lejeune to the South Carolina border, there have been 25 dolphin mortalities over the past six weeks. While the condition of the carcasses make it difficult to determine a cause of death for some, all of the animals that have been tested for the virus, have tested positive.

Dr. Vicky Thayer, the marine mammal stranding coordinator for the state’s central coast, said they have responded to 25 bottlenose dolphin stranding’s in the central region since August and the numbers have been increasing.

There have been 11 stranding’s across the central region so far in November, well above the average of three normally seen.

While not all of the dolphins found dead are tested for the virus, Thayer said they know the virus is present.

“We know it’s here and we know we are getting a higher number (of stranding’s),” she said.

The virus is also popping up in other species, though its effects on those populations remain unknown. In the past month, four humpback whales have washed ashore on the East Coast; tissue samples from three of them showed the presence of genetic material related to morbillivirus.

“The results show that they’ve been exposed,” McLellan said. “We haven’t seen it specifically causing a disease-like state like we have in bottlenose dolphins. It’s there, but we don’t understand morbillivirus in whales as well as we do in dolphins.”

The timing is potentially problematic. Calving season for the North Atlantic right whale begins in mid-November, meaning the mammals are currently on the move, migrating down the East Coast in search of warmer winter waters. There are fewer than 400 right whales in existence, making the species one of the most endangered marine mammals on the planet, according to the National Oceanic and Atmospheric Administration.

At this point, there’s nothing to suggest the virus has jumped to right whales, McLellan said. But the presence of the disease in humpbacks means it’s a possibility, particularly given the proximity of dolphins to right whales during their migrations.

“A whale swimming along looks just like a boat to a dolphin, and it’s not uncommon to see bottlenose dolphins riding along in front of one,” McLellan said. “There’s a large potential that right whales could be exposed to dolphins with morbillivirus. That’s the huge question right now.”

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